Electrical apparatus for gaseous discharge devices



July 27, 19 8. H. w. ALFORD 2,446,152

' ELECTRICAL APPARATUS FOR GASEOUS DISCHARGE DEVICES Filed May 29, 1946 ATTORNEY Patented July 27, 1948 Lit-6J5;

dietitian APPARATUS FOR GASEOUS DISCHARGE DEVICES Harold W. Alford, Danvers, Mass, assignor to Sylvania Electric Products Inc., Salem, Mass, a corporation of Massachusetts Application May 29, 1946, Serial No. 672,987

1 Claim. 1

This invention relates to electric gaseous discharge devices and more particularly to the electrical apparatus normally employed in conjunction therewith.

The electrical apparatus normally employed in a hot-cathode fluorescent lamp installation usually includes some means whereby a voltage higher than the line voltage of about 110-120 volts may be initially impressed across the lamp electrodes to bring them to electron-emitting temperatures.

Because of this requirement for higher potentials, consideration has to be given, in designing the electrical apparatus, to meeting certain safety rules and regulations, especially where domestic installations are concerned.

In the case of certain fluorescent lamps which are portable it has been found that higher potentials are usually required than code regulations governing portable lamps used in the home permit. In certain cases the lamp potential of 150 volts permitted by the code has been found to be too low to give satisfactory lamp performance.

The object of this invention is to provide a circuit arrangement which will permit an increase in the lamp potential high enough above 150 volts to accomplish satisfactory lamp operation and at the same time maintain the potential with respect to ground at or below 150 volts, the maximum permitted by safety regulations.

My invention embodies the idea of tapping an auto-transformer at two points intermediate its ends and connecting the line across the center section defined by the two tappings. A currentlimiting reactance may be placed in one lamp lead or half may be placed in each so that the current to ground will be limited in case of an accident. Alternatively a current-limiting reactance need not be used if a high reactance auto-transformer is used.

The principles herein set forth whereby the lamp potential may be increased substantially without changing the potential with respect to ground may well be applied to other specific embodiments without departing from the spirit of my invention.

Some of the embodiments of the principles of my invention are illustrated in the accompanying drawing in which:

Figure 1 is a circuit diagram illustrating the principles of my invention in which a current limiting reactance is disposed in one lamp lead.

Figure 2 is a circuit diagram in which a split choke is employed, and

Figure 3 is a circuit diagram in which a high reactance transformer is used.

In Figure 1 a 182 volt auto-transformer l is wound. and tapped 32 volts from each end and the line 2 is connected across the center 118 volt section 3. End 4 of the transformer I is connected to one end of a current limiting reactance, such as a choke coil 9. The other end of the coil ii is connected to an end of a filamentary electrode 6 in a fluorescent lamp 8. The end 5 of the transformer I is connect-ed to amend of a filamentary electrode 1 in the lamp 8. The other ends of the filamentary electrodes are connected to each other through a conventional lamp starter switch H3. One side of the line is grounded, i. e., either lead E3 or M, depending on how the connection is made. Thus the highest potential to ground is limited to volts despite the 182 volts available to start the lamp.

The circuit illustrated in Figure 2 is similar to the one illustrated in Figure 1 except that a current limiting reactance, such as a choke coil is disposed in each lamp lead. Thus, in addition to the choke coil 9 which is disposed between end 4 of the transformer I and an end of the filamentary electrode 6, an additional choke coil II is disposed between end 5 of the transformer l and an end of the filamentary electrode 1.

Then if, for example line l'3 were grounded, and the circuit became accidentally grounded at l5,

the fault current flowing would be limited by the choke coil H. Choke coil 9 would act similarly if M were the intentionally grounded line-and IS the accidentally grounded point.

In, the circuit illustrated in Figure3 a high reactance transformer I2 is employed. This permits the elimination of choke coils H and II.

My invention is not necessarily limited to use with hot cathode fluorescent lamps. It may be used with other electric gaseous discharge devices .without departing from the spirit of the invention.

What I claim is:

A circuit for an electric gaseous discharge device having an electrode disposed at each end thereof, said circuit comprising an auto-transformer, a current limiting reactance having one of the other of said electrodes, said auto-transformer being tapped at two places intermediate its ends and equi-distant therefrom, a source of electrical energy connected to said auto-transformer at the two tapped positions, one side of said source of electrical energy being grounded, and a starter switch connected across the other ends of said electrodes.

' HAROLD "W. ALFORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,264,055 Stocker Nov. 25, 1941 5 2,268,512 McCarthy Dec. 30, 1941 2,298,935 Freeman Oct. 13, 1942 2,351,616 Karash et a1. June 20, 1944 FOREIGN PATENTS m Number Country Date 203,789 Switzerland July 1, 1939 526,591 Great Britain Sept. 20, 1940 P? page 1332, 7th 6a., 1941,McGraw-Hil1,1nc., N. Y.

(Copy in Scientific Library.) 

